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Purpose:To report the clinical outcomes with 24-month follow-up of transepithelial cross-linking using a combination of a d-alpha-tocopheryl polyethylene-glycol 1000 succinate (vitamin E-TPGS)-enhanced riboflavin solution and abbreviated low fluence UV-A treatment.Methods:In a nonrandomized clinical trial, 25 corneas of 19 patients with topographically proven, progressive, mild to moderate keratoconus over the previous 6 months were cross-linked, and all patients were examined at 1, 3, 6, 12, and 24 months. The treatments were performed using a patented solution of riboflavin and vitamin E-TPGS, topically applied for 15 minutes, followed by two 5-minute UV-A treatments with separate doses both at fluence below 3 mW/cm2 that were based on preoperative central pachymetry.Results:During the 6-month pretreatment observation, the average Kmax increased by +1.99 ± 0.29 D (diopter). Postoperatively, the average Kmax decreased, changing by −0.55 ± 0.94 D, by −0.88 ± 1.02 D and by −1.01 ± 1.22 D at 6, 12, and 24 months. Postoperatively, Kmax decreased in 19, 20, and 20 of the 25 eyes at 6 months, 12 months, and 24 months, respectively. Refractive cylinder was decreased by 3 months postoperatively and afterward, changing by −1.35 ± 0.69 D at 24 months. Best spectacle-corrected visual acuity (BSCVA) improved at 6, 12, and 24 months, including an improvement of −0.19 ± 0.13 logarithm of the minimum angle of resolution units at 24 months. There was no reduction in endothelial cell count. No corneal abrasions occurred, and no bandage contact lenses or prescription analgesics were used during postoperative recovery.Conclusions:Transepithelial cross-linking using the riboflavin-vitamin E solution and brief, low-dose, pachymetry-dependent UV-A treatment safely stopped keratoconus progression.

The experimental and mathematical analyses establish the basis for graphs that prescribe maximum safe fluence and UV-A exposure time for corneas of different thicknesses. Because this clinically tested protocol specifies a corneal surface clear of shielding riboflavin on the corneal surface during UV-A irradiation, it allows for shorter UV-A irradiation time and lower fluence than in the Dresden protocol.

To evaluate the efficiency and safety of iontophoretic transepithelial corneal crosslinking in pediatric patients with progressive keratoconus underwent general or topical anesthesia in 18 months follow-up. 13 patients (13 eyes) diagnosed with progressive keratoconus underwent corneal CXL with iontophoresis (I-CXL). Riboflavin solution was administered by iontophoresis for 5 min, and then UV-A irradiation (10 mW/cm) was performed for 9 min. Preoperative and post-operative visits at 1, 6, 12, and 18 months assessed the following parameters: uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), slit-lamp biomicroscopy, corneal topography, optical tomography, and pachymetry with Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany), endothelial biomicroscopy (Konan Specular Microscope; Konan Medical, Inc., Hyogo, Japan). The paired Student t test was used to compare data during the follow-up. 10 males and 3 females with a mean age of 15.4 ± 1.7 years (range 11-18 years) were included. The results showed a stabilization of the refractive UCVA and BCVA as early as the first post-operative month, with a slight improvement over time. The Kmax remained stable throughout follow-up (p = 0.04). Transepithelial collagen crosslinking by iontophoresis, unlike other transepithelial techniques seems to halt pediatric keratoconus progression over 18 months. This is the second study evaluating CXL with iontophoresis in pediatric patients with progressive keratoconus with 18 months of follow-up using two different ways of anesthesia.

Purpose:To determine the cross-linking effect of a riboflavin ultraviolet-A (UV-A) corneal cross-linking treatment that is both shorter and has lower energy than the Dresden protocol.Methods:In a first experiment, 12 human corneas were presoaked with riboflavin and then irradiated with UV-A at 3 mW/cm2 after clearing the surface of riboflavin, with no added riboflavin during irradiation. Percent UV-A transmission through the corneas was measured at intervals up to 30 minutes. A second experiment involved 24 porcine corneas. Eight were de-epithelialized, presoaked in riboflavin for 30 minutes, and irradiated at 1.5 mW/cm2 for 10 minutes. An additional 8 were riboflavin treated and similarly irradiated, but with epithelium intact and a final 8 corneas were not treated. Young modulus was measured in all 24 corneas at the end of the experiment.Results:The first experiment showed essentially complete riboflavin oxidation after only 10 minutes. Based on these results, a shortened UV-A exposure cross-linking experiment was designed using a reduced UV-A fluence of 1.5 mW/cm2, an endothelial exposure within safety limits in humans. With this protocol Young modulus was the same in the irradiated porcine corneas but with epithelium intact as in the untreated corneas. In contrast, Young modulus increased by a factor of 1.99 in the UV-A cross-linked corneas at 1.5 mW/cm2 for 10 minutes with the epithelium removed.Conclusions:A shorter, lower energy protocol than the Dresden protocol seems to provide a significant increase in Young modulus, similar to published results with higher energy, longer exposure protocols.